Latanoprost has a chemical name of isopropyl-(Z)-7-[(1R,2R,3R,5S)3,5-dihydroxy-2-[(3R)-3-hydroxy-5-phenylpentyl]cyclopentyl]-5-heptenoate and is used as a prostaglandin analog for the treatment of glaucoma. The administration route of latanoprost is ocular instillation and an ophthalmic solution containing 0.005% of latanoprost is commercially available. However, latanoprost itself is a thermally unstable drug and tends to decompose in an ophthalmic solution when temperature becomes higher than normal temperature (25° C.). For this reason, a latanoprost-containing ophthalmic solution has to be stored in a cold place (2 to 8° C.) under light shielding. NON-PATENT LITERATURE 1 is an article which reports the stability of a latanoprost-containing ophthalmic solution to temperature and light.
As for a latanoprost-containing ophthalmic solution, its storage temperature may increase during distribution or storage in some cases and decomposition of a part of latanoprost is therefore unavoidable. As far as a latanoprost-containing ophthalmic solution is stored in a cold place, the decomposition of thermally unstable latanoprost can be controlled. Since such an ophthalmic solution is exposed to various environments, however, the development of technology which prevents the decomposition of latanoprost by a method other than cold storage is desired.